Thanks for the question! So we’re asked here about the author’s reference to the Fur Seal Treaty in line 22, so we go to that line, and we make sure to read at least a few lines above and below to understand the full context of the Fur Seal Treaty and why it’s used. Here, even, we should probably read the entire third paragraph to understand the entire context of the paragraph. If we do, we learn that the main point of the third paragraph is to go through the legal history of Native Alaskans’ legal rights to engage in traditional practices (like seal hunting), and this is what (E) tells us.
(C), on the other hand, is wrong because nothing tells us that there’s the Fur Seal Treaty is well-known, or is legal precedent. And in addition, that’s not the primary usage of the reference to the Fur Seal Treaty anyway (always keep in mind what the question is asking), and so (C) can’t be right.
Hope this helps! Feel free to ask any other questions that you might have.